what do fluorescent probes have to do with increasing resolution?

Question: what do fluorescent probes have to do with increasing resolution?
- Keywords:
  fluorescent,
  probes,
  resolution
Asked by blytheacres to Chris on 19 Jun 2012.
- Chris Kettle answered on 19 Jun 2012:
  
  Fluorescent probes let you test areas of DNA that are smaller than you can see with the human eye using a microscope. These means we can look at smaller pieces of DNA, and this means we increase our resolution.

Question: what do fluorescent probes have to do with increasing resolution?